This invention relates to a panel for self-supporting roof structures of the type comprising elongated extruded, preferably translucent, profile elements of plastics material, in particular polycarbonate, each having at least one main duct and on the outer sides coupling members for securing one profile element side by side to adjacent similar profile elements so as to form a continuous surface requiring support only along two opposite ends. Such panels may have an intermediate wall dividing the main duct of the profile element into two subducts disposed in succession in the direction from the inner side of the outer side of the profile element.
Prior art profile elements of the type in question are shown by way of example in the British Pat. Nos. 901,935 and 1,511,189 and a development of such elements is disclosed in the co-pending application Ser. No. 300 510.
A self-supporting roof made of such profile elements possesses good insulating properties, especially when the ducts are closed at their ends, which is normally done by means of small blocks of insulating material cut so as to fit into the ducts. The insulating material prevent free air circulation but allow some air exchange. This closing method presents a number of disadvantages. Even when choosing an insulating material of a colour matching that of the profile element so that it is only slightly noticeable, it becomes dirty after some time and spoils the appearance of the roof. Furthermore, the material is exposed to damage and may fall out under the action of variable loads and fluctuations of temperature.